Source : Webster's Revised Unabridged Dictionary (1913)

Knack \Knack\, v. i. [Prob. of imitative origin; cf. G. knacken
   to break, Dan. knage to crack, and E. knock.]
   1. To crack; to make a sharp, abrupt noise to chink. [Obs. or
      Prov. Eng.] --Bp. Hall.

   2. To speak affectedly. [Prov. Eng.] --Halliwell.

Knack \Knack\, n.
   1. A petty contrivance; a toy; a plaything; a knickknack.

            A knack, a toy, a trick, a baby's cap. --Shak.

   2. A readiness in performance; aptness at doing something;
      skill; facility; dexterity.

            The fellow . . . has not the knack with his shears.
                                                  --B. Jonson.

            The dean was famous in his time, And had a kind of
            knack at rhyme.                       --Swift.

   3. Something performed, or to be done, requiring aptness and
      dexterity; a trick; a device. ``The knacks of japers.''
      --Chaucer.

            For how should equal colors do the knack ! --Pope.

Source : WordNet®

knack
     n : a special way of doing something; "he had a bent for it";
         "he had a special knack for getting into trouble"; "he
         couldn't get the hang of it" [syn: {bent}, {hang}]